Three core functions of EV lithium ion battery BMS

1) Cell monitoring technology

1. Single cell voltage acquisition; 2. Cell temperature acquisition; 3. Battery current detection;

Accurate temperature measurement is also very important for the working state of the battery pack, including the temperature measurement of a single battery and the temperature monitoring of the cooling liquid of the battery pack. The position and number of temperature sensors should be reasonably set to form a good cooperation with BMS control module. The key point of monitoring the temperature of cooling liquid of battery pack is the fluid temperature of inlet and outlet, and the selection of monitoring accuracy is similar to that of single battery.


2) SOC (state of charge) technology: simply put, how much power is left in the battery

SOC is the most important parameter in BMS. Because everything else is based on SOC, its accuracy and robustness (also known as error correction ability) are extremely important. If there is no accurate SOC, no matter how many protection functions can not make the BMS work normally, because the battery will always be in the protected state, and can not prolong the battery life.

The higher the accuracy of SOC estimation, the higher the range of electric vehicle can be obtained with the same capacity of battery. High precision SOC estimation can maximize the battery pack performance.


3) Balance technology

Passive balance usually uses the way of resistance heat release to release the extra power of high-capacity battery, so as to achieve the purpose of balance. The circuit is simple and reliable, the cost is low, but the battery efficiency is also low.

In active balance charging, the surplus power is transferred to the high capacity cell, while the excess power is transferred to the low capacity cell when discharging, which can improve the use efficiency, but the cost is higher, the circuit is complex and the reliability is low. In the future, with the improvement of cell consistency, the demand for passive balance may decrease.